Recommendations for the classification of diseases as CFTR-related disorders

Cystic Fibrosis: A Journey through Time and Hope

Just over thirty years is the span of a generation. It is also the time that has passed since the discovery of the gene responsible for cystic fibrosis. Today, it is safe to say that this discovery has revolutionized our understanding, research perspectives, and management of this disease, which was, thirty years ago, a pediatric condition with a grim prognosis. The aim of this review is to present the advances that science and medicine have brought to our understanding of the pathophysiology of the disease and its management, which in many ways, epitomizes modern molecular genetic research. Since the discovery of the cystic fibrosis transmembrane conductance regulator (CFTR) gene in 1989, modeling the CFTR protein, deciphering its function as an ion channel, and identifying its molecular partners have led to numerous therapeutic advances. The most significant advancement in this field has been the discovery of protein modulators that can target its membrane localization and chloride channel activity. However, further progress is needed to ensure that all patients can benefit from a therapy tailored to their mutations, with the primary challenge being the development of treatments for mutations leading to a complete absence of the protein. The present review delves into the history of the multifaceted world of CF, covering main historical facts, current landscape, clinical management, emerging therapies, patient perspectives, and the importance of ongoing research, bridging science and medicine in the fight against the disease.

Biochemical and genetic tools to predict the progression to Cystic Fibrosis in CRMS/CFSPID subjects: A systematic review

OBJECTIVES

Aim of this study was to identify risk factors for a progression to cystic fibrosis (CF) in individuals detected as CF Screening Positive, Inconclusive Diagnosis (CFSPID).

METHODS

This is a systematic review through literature databases (2015-2023). Blood immunoreactive trypsinogen (b-IRT) values, CFTR genotype, sweat chloride (SC) values, isolation of Pseudomonas aeruginosa (Pa) from respiratory samples, Lung Clearance Index (LCI) values in CFSPIDs who converted to CF (CFSPID > CF) and age at CF transition were assessed.

RESULTS

Percentage of CFSPID > CF varies from 5.3 % to 44 %. Presence of one CF-causing CFTR variant in trans with a variant with variable clinical consequences (VVCC), an initial SC ≥ 40 mmol/L, an increase of SC > 2.5 mmol/L/year and recurrent isolation of pseudomonas aeruginosa (Pa) from airway samples could allow identification of subjects at risk of progression to CF.

CONCLUSIONS

CFSPIDs with CF causing variant/VVCC genotype and first SC in the higher borderline range may require more frequent and prolonged clinical follow-up.

The novel CFTR haplotype E583G/F508del in CFTR-related disorder

BACKGROUND

CFTR-related disorder (CFTR-RD) is a clinical entity associated to complex diagnostic paths and newly upgraded standard of care. In CFTR-RD, CFTR genotyping represents a diagnostic surrogate marker. In case of novel haplotype, the diagnosis could represents an area of concern. We described the molecular evaluation of the rare CFTR variant E583G identified in trans with the F508del in a novel haplotype.

METHODS AND RESULTS

An adult woman was referred to our pulmonary unit for persistent respiratory symptoms. CFTR Next Generation Sequencing was performed to evaluate full-gene mutational status. The variant identified was evaluated for its pathogenicity integrating clinical evidences with dedicated bioinformatics analyses. Clinical evaluation of patient matched with a mono-organ CFTR-RD diagnosis. Genotyping revealed the novel CFTR haplotype F508del/E583G. Multiple evidences of a deleterious effect of the CFTR E583G rare variant emerged from the bioinformatics analyses performed.

CONCLUSIONS

Guidelines for CFTR-RD are available with the purpose of harmonizing clinical and molecular investigations. In such context, the identification of novel CFTR haplotype need to a deeper evaluation with a combination of skills. The novel E583G variant could be considered of clinical interest and overall a CFTR-RD Variants of Varying Clinical Consequences.

Challenges of Preimplantation Genetic Counselling in the Context of Cystic Fibrosis and Other CFTR-Related Disorders: A Monocentric Experience in a Cohort of 92 Couples

Cystic fibrosis is a highly prevalent genetic disorder caused by biallelic pathogenic variants in the CFTR gene, causing an altered function of the exocrine glands and a subsequent spectrum of hypofunctional and degenerative manifestations. The increasing availability of carrier screening programmes, the enhanced life expectancy of patients due to improved treatment and care strategies and the development of more precise and affordable molecular diagnostic tools have prompted a rise in demand of prenatal diagnosis procedures for at-risk couples, including Preimplantation Genetic Testing (PGT). However, challenges remain: heterogeneity among screening programmes, nuances of variant interpretation and availability of novel treatments demand a considerate and knowledgeable approach to genetic counselling. In this work, we retrospectively evaluated the molecular data of 92 unselected couples who received a diagnosis of CFTR-related status and were referred to the genetics clinic at the University Hospital of Padua for genetic counselling on eligibility for PGT. A total of 50 couples were considered eligible for the procedure based on risk of transmitting biallelic pathogenic variants. We report and discuss our experience with this case series in the context of the Italian medical care system and present an overview of the most relevant issues regarding genetic counselling for PGT in CFTR-related disorders.

Molecular diagnosis of cystic fibrosis by RNA obtained from nasal epithelial cells

BACKGROUND

The diagnosis of cystic fibrosis (CF) is established when characteristic clinical signs are coupled with biallelic CFTR pathogenic variants. No previously reported non-canonical splice site variants have to be considered as variants of uncertain significance unless their effect on splicing has been validated.

METHODS

Two variants identified by next-generation sequencing were evaluated. We assayed their effects on splicing employing RNA analysis and real-time expression quantification from RNA obtained from the nasal epithelial cells of a patient with clinically suspected CF and of two patients with milder phenotypes (CFTR-related disorders).

RESULTS

The variant c.164+2dup causes skipping of exon 2 (p.(Ser18_Glu54del)) and exon 2 plus 3 (p.(Ser18Argfs*16)) in CFTR mRNA. Exon 2 expression in the patient heterozygous for c.164+2dup was decreased to 7 % of the exon 2 expression in the controls. The synonymous variant c.1584G>A causes a partial skipping of exon 11. The exon 11 expression in the two patients heterozygous for this variant was 22 % and 42 % of that of the controls, respectively.

CONCLUSION

We conclude that variant c.164+2dup affects mRNA processing and can be considered a CF-causing variant. The results of the functional assay also showed that the p.(Glu528=) variant, usually categorized as a neutral variant based on epidemiological data, partially affects mRNA processing in our patients. This finding would allow us to reclassify the variant as a CFTR-related variant with incomplete penetrance. RNA obtained from nasal epithelial cells is an easy and accurate tool for CFTR functional studies in patients with unclassified splice variants.

Diagnosis of cystic fibrosis: a high heterogeneity of symptoms and genotypes in a Brazil population

INTRODUCTION

In highly multiracial populations with inadequate newborn screening, knowledge of the various phenotypic presentations of Cystic Fibrosis (CF) can help reach an early diagnosis. This study aims to describe phenotypes and genotypes at the time of CF diagnosis in a state in the Northeast Region of Brazil.

METHODS

Retrospective cross-sectional study. Clinical data were extracted from the medical records of CF patients. Clinical, laboratory, and genotypic characteristics were described for patients admitted to a tertiary referral center between 2007 and 2021.

RESULTS

Fifty-eight (58) patients were included in the study, 53.5% of whom were diagnosed through clinical suspicion. The median age at diagnosis was 4.7 months (IQR: 1.5-14.8 months). Five patients had false-negative results in the newborn screening. Faltering growth was the most frequent clinical manifestation. Bronchiectasis and a history of pneumonia predominated in those older than ten, while thinness, underweight, and electrolyte imbalances were more frequent in children under two. Sequencing of the CFTR gene identified 27 genotypes, with at least one class I-III variant in all patients, and nine variants that are rare, previously undescribed, or have uncertain significance (619delA, T12991, K162Q, 3195del6, 1678del > T, 124del123bp, 3121-3113 A > T). The most frequent alleles were p.Phe508del, p.Gly542*, p.Arg334Trp, and p.Ser549Arg.

CONCLUSIONS

Malnutrition and electrolyte imbalances were the most frequent phenotypes for children < 2 years and were associated with genotypes including 2 class I-III variants. Rare and previously undescribed variants were identified. The p.Gly542*, p.Arg334Trp, and p.Ser549Arg alleles were among the most frequent variants in this population.

Update on advances in cystic fibrosis towards a cure and implications for primary care clinicians

During the past quarter century, the diagnosis and treatment of cystic fibrosis (CF) have been transformed by molecular sciences that initiated a new era with discovery of the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The knowledge gained from that breakthrough has had dramatic clinical impact. Although once a diagnostic dilemma with long delays, preventable deaths, and irreversible pathology, CF can now be routinely diagnosed shortly after birth through newborn screening programs. This strategy of pre-symptomatic identification has eliminated the common diagnostic "odyssey" that was a failure of the healthcare delivery system causing psychologically traumatic experiences for parents. Therapeutic advances of many kinds have culminated in CFTR modulator treatment that can reduce the effects of or even correct the molecular defect in the chloride channel -the basic cause of CF. This astonishing advance has transformed CF care as described fully herein. Despite this impressive progress, there are challenges and controversies in the delivery of care. Issues include how best to achieve high sensitivity newborn screening with acceptable specificity; what course of action is appropriate for children who are identified through the unavoidable incidental findings of screening tests (CFSPID/CRMS cases and heterozygote carriers); how best to ensure genetic counseling; when to initiate the very expensive but life-saving CFTR modulator drugs; how to identify new CFTR modulator drugs for patients with non-responsive CFTR variants; how to adjust other therapeutic modalities; and how to best partner with primary care clinicians. Progress always brings new challenges, and this has been evident worldwide for CF. Consequently, this article summarizes the major advances of recent years along with controversies and describes their implications with an international perspective.

CFTR function is impaired in a subset of patients with pancreatitis carrying rare CFTR variants

BACKGROUND

Many affected by pancreatitis harbor rare variants of the cystic fibrosis (CF) gene, CFTR, which encodes an epithelial chloride/bicarbonate channel. We investigated CFTR function and the effect of CFTR modulator drugs in pancreatitis patients carrying CFTR variants.

METHODS

Next-generation sequencing was performed to identify CFTR variants. Sweat tests and nasal potential difference (NPD) assays were performed to assess CFTR function in vivo. Intestinal current measurement (ICM) was performed on rectal biopsies. Patient-derived intestinal epithelial monolayers were used to evaluate chloride and bicarbonate transport and the effects of a CFTR modulator combination: elexacaftor, tezacaftor and ivacaftor (ETI).

RESULTS

Of 32 pancreatitis patients carrying CFTR variants, three had CF-causing mutations on both alleles and yielded CF-typical sweat test, NPD and ICM results. Fourteen subjects showed a more modest elevation in sweat chloride levels, including three that were provisionally diagnosed with CF. ICM indicated impaired CFTR function in nine out of 17 non-CF subjects tested. This group of nine included five carrying a wild type CFTR allele. In epithelial monolayers, a reduction in CFTR-dependent chloride transport was found in six out of 14 subjects tested, whereas bicarbonate secretion was reduced in only one individual. In epithelial monolayers of four of these six subjects, ETI improved CFTR function.

CONCLUSIONS

CFTR function is impaired in a subset of pancreatitis patients carrying CFTR variants. Mutations outside the CFTR locus may contribute to the anion transport defect. Bioassays on patient-derived intestinal tissue and organoids can be used to detect such defects and to assess the effect of CFTR modulators.

ECFS standards of care on CFTR-related disorders: Towards a comprehensive program for affected individuals

After three publications defining an updated guidance on the diagnostic criteria for people with cystic fibrosis transmembrane conductance regulator (CFTR)-related disorders (pwCFTR-RDs), establishing its relationship to CFTR-dysfunction and describing the individual disorders, this fourth and last paper in the series addresses some critical challenges facing health care providers and pwCFTR-RD. Topics included are: 1) benefits and obstacles to collect data from pwCFTR-RD are discussed, together with the opportunity to integrate them into established CF-registries; 2) the potential of infants designated CRMS/CFSPID to develop a CFTR-RD and how to communicate this information; 3) a description of the challenges in genetic counseling, with particular regard to phenotypic variability, unknown long-term evolution, CFTR testing and pregnancy termination 4) a proposal for the assessment of potential barriers to the implementation and dissemination of the produced documents to health care professionals involved in the care of pwCFTR-RD and a process to monitor the implementation of the CFTR-RD recommendations; 5) clinical trials investigating the efficacy of CFTR modulators in CFTR-RD and how endpoints and outcomes might be adapted to the heterogeneity of these disorders.

Cystic Fibrosis Foundation Evidence-Based Guideline for the Management of CRMS/CFSPID

A multidisciplinary committee developed evidence-based guidelines for the management of cystic fibrosis transmembrane conductance regulator-related metabolic syndrome/cystic fibrosis screen-positive, inconclusive diagnosis (CRMS/CFSPID). A total of 24 patient, intervention, comparison, and outcome questions were generated based on surveys sent to people with CRMS/CFSPID and clinicians caring for these individuals, previous recommendations, and expert committee input. Four a priori working groups (genetic testing, monitoring, treatment, and psychosocial/communication issues) were used to provide structure to the committee. A systematic review of the evidence was conducted, and found numerous case series and cohort studies, but no randomized clinical trials. A total of 30 recommendations were graded using the US Preventive Services Task Force methodology. Recommendations that received ≥80% consensus among the entire committee were approved. The resulting recommendations were of moderate to low certainty for the majority of the statements because of the low quality of the evidence. Highlights of the recommendations include thorough evaluation with genetic sequencing, deletion/duplication analysis if <2 disease-causing variants were noted in newborn screening; repeat sweat testing until at least age 8 but limiting further laboratory testing, including microbiology, radiology, and pulmonary function testing; minimal use of medications, which when suggested, should lead to shared decision-making with families; and providing communication with emphasis on social determinants of health and shared decision-making to minimize barriers which may affect processing and understanding of this complex designation. Future research will be needed regarding medication use, antibiotic therapy, and the use of chest imaging for monitoring the development of lung disease.

Diagnostic challenges in CFTR-related metabolic syndrome: Where the guidelines fall short

Newborn screening (NBS) for cystic fibrosis (CF) has enabled earlier diagnosis and has improved nutritional and growth-related outcomes in children with CF. For those with a positive NBS for CF that do not meet the diagnostic criteria for CF, the clinical entity called CFTR-Related Metabolic Syndrome (CRMS) or CF Screen- Positive, Inconclusive Diagnosis (CFSPID) is used. Although most children with CRMS remain relatively asymptomatic, studies have shown that between 11% and 48% of these patients may eventually progress to a diagnosis of CF over time. Although the CF Foundation guidelines for CRMS management and European CF Society guidelines for CFSPID have some similarities, there are also some differences. Here, we review challenging case scenarios that highlight remaining gaps in CRMS guidelines, thus supporting the need to update and unify existing guidelines.

Unmet challenges in cystic fibrosis treatment with modulators

INTRODUCTION

'Highly effective' modulator therapies (HEMTs) have radically changed the Cystic Fibrosis (CF) therapeutic landscape.

AREAS COVERED

A comprehensive search strategy was undertaken to assess impact of HEMT in life of pwCF, treatment challenges in specific populations such as very young children, and current knowledge gaps.

EXPERT OPINION

HEMTs are prescribed for pwCF with definite genotypes. The heterogeneity of variants complicates treatment possibilities and around 10% of pwCF worldwide remains ineligible. Genotype-specific treatments are prompting theratyping and personalized medicine strategies. Improvement in lung function and quality of life increase survival rates, shifting CF from a pediatric to an adult disease. This implies new studies addressing long-term efficacy, side effects, emergence of adult co-morbidities and possible drug-drug interactions. More sensitive and predictive biomarkers for both efficacy and toxicity are warranted. As HEMTs cross the placenta and are found in breast milk, studies addressing the potential consequences of treatment during pregnancy and breastfeeding are urgently needed. Finally, although the treatment and expected outcomes of CF have improved dramatically in high- and middle-income countries, lack of access in low-income countries to these life-changing medicines highlights inequity of care worldwide.

An overview of CFTR mutation profiles and assisted reproductive technology outcomes in Chinese patients with congenital obstructive azoospermia

PURPOSE

The cystic fibrosis transmembrane conductance regulator (CFTR) is the most common causative gene attributed to congenital obstructive azoospermia (OA). The aim of this study was to conduct an epidemiological survey of congenital OA patients, to screen for CFTR mutations, and to follow their pregnancy outcomes in assisted reproductive technology (ART).

METHODS

This cohort study enrolled congenital OA patients undergoing ART and whole-exome sequencing from January 2018 to September 2023. Semen parameters, sex hormones, and seminal plasma biochemistry were evaluated. CFTR mutations identified in OA patients were analyzed. In addition, the laboratory outcomes, clinical outcomes, and neonatal outcomes were compared between OA patients carrying two CFTR mutations and the others after surgical sperm extraction-intracytoplasmic sperm injection (ICSI) treatment.

RESULTS

A total of 76 patients with congenital OA were enrolled. CFTR mutations were identified in 35 (46.1%) congenital OA patients. A total of 60 CFTR mutation sites of 27 types were identified, and 10 of them were novel. The average frequency was 1.71 (60/35) per person. The most common mutation was c.1210-11T > G (25%, 15/60). After ICSI treatment, there were no statistically significant differences in laboratory outcomes, clinical outcomes, and neonatal outcomes between OA patients carrying two CFTR mutations (n = 25) and other OA patients (n = 51).

CONCLUSION

Apart from the IVS9-5T mutation, the genetic mutation pattern of CFTR in Chinese OA patients is heterogeneous, which is significantly different from that of Caucasians. Although carrying two CFTR mutations or not had no effect on the pregnancy outcomes in OA patients after ICSI, genetic counseling is still recommended for such patients.

A Unique Mutation in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Gene Causing Cystic Fibrosis in a Pakistani Child: A Case Highlighting the Need for More Awareness

Cystic fibrosis (CF) is a recessively inherited disease most commonly seen in Caucasians. The mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene are responsible for the condition, and to date, more than 2000 mutations have been published in the literature. The most common mutation worldwide is F508del. Here, we reported a five-year-old child who presented to the clinic with a chronic cough. Her newborn screening for CF was negative, including 139 mutation panels done in India. The sweat chloride test was positive, and CF gene sequencing was reported as c.2489dup p. (Glu831GLYFS *5) homozygotes mutation in the CFTR gene (Online Mendelian Inheritance in Man (OMIM) *602421). To the best of our knowledge, this gene was first described and published in the literature.

Risk of CFTR-related disorders and cystic fibrosis in an Italian cohort of CRMS/CFSPID subjects in preschool and school age

The identification of cystic fibrosis screening-positive, inconclusive diagnosis (CFSPID) in infants is a controversial outcome of newborn screening for cystic fibrosis (CF). Today, despite improvements in the knowledge of CFSPID and the description of several cohorts, little data are available on cohorts with a follow-up period of more than 6 years. In this study, we report the outcomes of an Italian cohort of CFSPID individuals with CFSPID or formerly CFTR-related disorders (CFTR-RD) (CFSPID > CFTR-RD) or diagnosed with CF (CFSPID > CF). This was an observational and multicentre Italian study collecting clinical data on CFSPID born between the period January 1, 2011, and December 13, 2019. A total of 268 participants were included: 243 with persistent CFSPID, 7 with CFSPID > CFTR-RD, and 18 with CFSPID > CF. The trend of sweat chloride (SC) values, percentage of definitive diagnoses, lung function in school-aged children, and development of CF-related complications were evaluated. At the end of the observation period, almost 80% of the individuals with CFSPID did not have a conclusive diagnosis. A total of 29 children (10.8%) transitioned to a diagnosis of CF for pathological SC values (≥ 60 mmol/L) or multi-organ involvement, and 18 (6.7%) to CFTR-RD. Children who were followed up for > 6 years (median age, 7.5 years; range, 6.04-10.5) had normal lung function and were pancreatic sufficient, and the evolution in CF was only present in two cases.

CONCLUSION

Most Italian preschool and school-aged children with CFSPID did not have a conclusive diagnosis, and progression to CF was unlikely in children > 6 years of age. An annual follow-up could be indicated to identify early evolution in clinical features consistent with a CFTR-RD.

WHAT IS KNOWN

• Cystic Fibrosis newborn screening identifies also subjects with an inconclusive diagnosis (CFSPID). • Over time a variable percentage of CFSPIDs will be diagnosed as CF. • Little data is available on CFSPIDs with a follow-up period of more than six years.

WHAT IS NEW

• 80% of Italian preschool and school-age CFSPIDs not have a conclusive diagnosis. • Italian preschool and school-age CFSPIDs have normal lung function and are pancreatic sufficient. • Annual follow-up after 6 years is recommended in CFSPID with abnormal LCI2.5 or with a CF-causing variant in trans with a VVCC.

Cystic fibrosis and CFTR-related disorder with electrolyte imbalance at diagnosis: clinical features and outcome in an Italian cohort

There is limited information available on the clinical data, sweat test trends, and outcomes of individuals with cystic fibrosis (CF) who present with an isolated episode of hypoelectrolytemia with metabolic alkalosis (HMA). This study describes a cohort of Italian individuals with HMA as presenting symptom. The study is a retrospective multicenter analysis of individuals who presented with HMA as an initial symptom and was followed at 8 Italian CF Centers, from March 1988 to March 2022. Demographic, clinical, microbiological, biochemical, and genetic data were extracted from local health records. Ninety-three individuals were enrolled in the study. At first evaluation, 82 (88.2%) were diagnosed with CF, and 11 received a CFTR-Related Disorder (CFTR-RD) diagnostic label. Twenty-three (85.1%) out of the 27 subjects who underwent CF neonatal screening (NBS) resulted falsely negative. After a mean observational period of 11.5 years, most of subjects had a mild pulmonary phenotype, pancreatic sufficiency, and rarely CF-related complications. Four CFTR-RD changed to a CF diagnosis during the study period, resulting in 86 (92.4%) subjects classified as CF.

CONCLUSIONS

 Most CF patients presenting with isolated HMA have a mild course of disease and rarely CF-related complications.

WHAT IS KNOWN

• Isolated episode of hypoelectrolytemia with metabolic alkalosis is a well-known onset symptom of Cystic Fibrosis in infancy. • There is limited information available on the clinical data and outcomes of individuals with Cystic Fibrosis who present with electrolyte imbalance at diagnosis.

WHAT IS NEW

• Most patients with Cystic Fibrosis presenting with isolated hypoelectrolytemia and metabolic alkalosis have a mild course of disease and rarely CF-related complications. • Electrolyte imbalance at diagnosis of Cystic Fibrosis is a common symptom in children not screened for CF at birth, or in those who received a false negative result from newborn screening.

Pathogenic Variants and Genotypes of the CFTR Gene in Russian Men with Cystic Fibrosis and CBAVD Syndrome

Pathogenic CFTR variants cause cystic fibrosis (CF), and CF-related disorders (CF-RD), including bilateral aplasia of the vas deferens (CBAVD). The spectrum of clinical manifestations depends on the CFTR genotype. The frequency and spectrum of the CFTR variants vary between populations and clinical groups. CFTR variants and genotypes were analyzed in Russian men with CF (n = 546) and CBAVD syndrome (n = 125). Pathogenic variants were detected in 93.95% and 39.2% of the CF and CBAVD alleles, respectively. The most frequent c.1521_1523del (F508del; p.Phe508del) variant was found in 541 (49.5%) CF alleles. A total of 162 CFTR genotypes were revealed in CF patients, including 152 homozygous and 394 compound-heterozygous. The most common CF-genotype was F508del/F508del (24.9%). Other frequent CF-genotypes were F508del/3849+10kbC>T, F508del/CFTRdele2,3, and F508del/E92K. CF-causing variants and/or 5T allele were found in 88% of CBAVD patients: 5T/CFTRmut (48.0%), CFTRmut/N (17.6%), CFTRmut/CFTRmut (6.4%), 5T/5T (10.4%), 5T/N (5.6%) and N/N (12.0%), with the most common CBAVD-genotype being F508del/5T (29.6%). The allele frequencies of F508del, CFTRdele2,3 394delTT, and 3849+10kbC>T were significantly higher in CF patients. L138ins/L138ins, 2184insA/E92K, and L138ins/N genotypes were found in CBAVD, but not in CF patients. The results indicate certain differences in the frequency of some CFTR variants and genotypes in Russian CF and CBAVD patients.

Standards for the care of people with cystic fibrosis (CF): A timely and accurate diagnosis

There is considerable activity with respect to diagnosis in the field of cystic fibrosis (CF). This relates primarily to developments in newborn bloodspot screening (NBS), more extensive gene analysis and improved characterisation of CFTR-related disorder (CFTR-RD). This is particularly pertinent with respect to accessibility to variant-specific therapy (VST), a transformational intervention for people with CF with eligible CFTR gene variants. This advance reinforces the need for a timely and accurate diagnosis. In the future, there is potential for trials to assess effectiveness of variant-specific therapy for CFTR-RD. The guidance in this paper reaffirms previous standards, clarifies a number of issues, and integrates emerging evidence. Timely and accurate diagnosis has never been more important for people with CF.

Clinical and genetic features of cystic fibrosis in Japan

Cystic fibrosis (CF) is an autosomal recessive disease caused by pathogenic variants in CF transmembrane conductance regulator (CFTR). While CF is the most common hereditary disease in Caucasians, it is rare in East Asia. In the present study, we have examined clinical features and the spectrum of CFTR variants of CF patients in Japan. Clinical data of 132 CF patients were obtained from the national epidemiological survey since 1994 and CF registry. From 2007 to 2022, 46 patients with definite CF were analyzed for CFTR variants. All exons, their boundaries, and part of promoter region of CFTR were sequenced and the presence of large deletion and duplications were examined by multiplex ligation-dependent probe amplification. CF patients in Japan were found to have chronic sinopulmonary disease (85.6%), exocrine pancreatic insufficiency (66.7%), meconium ileus (35.6%), electrolyte imbalance (21.2%), CF-associated liver disease (14.4%), and CF-related diabetes (6.1%). The median survival age was 25.0 years. The mean BMI percentile was 30.3%ile in definite CF patients aged < 18 years whose CFTR genotypes were known. In 70 CF alleles of East Asia/Japan origin, CFTR-dele16-17a-17b was detected in 24 alleles, the other variants were novel or very rare, and no pathogenic variants were detected in 8 alleles. In 22 CF alleles of Europe origin, F508del was detected in 11 alleles. In summary, clinical phenotype of Japanese CF patients is similar to European patients, but the prognosis is worse. The spectrum of CFTR variants in Japanese CF alleles is entirely different from that in European CF alleles.

Tissue-Specific Regulation of CFTR Gene Expression

More than 2000 variations are described within the CFTR (Cystic Fibrosis Transmembrane Regulator) gene and related to large clinical issues from cystic fibrosis to mono-organ diseases. Although these CFTR-associated diseases have been well documented, a large phenotype spectrum is observed and correlations between phenotypes and genotypes are still not well established. To address this issue, we present several regulatory elements that can modulate CFTR gene expression in a tissue-specific manner. Among them, cis-regulatory elements act through chromatin loopings and take part in three-dimensional structured organization. With tissue-specific transcription factors, they form chromatin modules and can regulate gene expression. Alterations of specific regulations can impact and modulate disease expressions. Understanding all those mechanisms highlights the need to expand research outside the gene to enhance our knowledge.

Gradual increase in sweat chloride concentration is associated with a higher risk of CRMS/CFSPID to CF reclassification

OBJECTIVES

Universal implementation of cystic fibrosis (CF) newborn screening (NBS) has led to the diagnostic dilemma of infants with CF screen-positive, inconclusive diagnosis (CFSPID), with limited guidance regarding prognosis and standardized care. Rates of reclassification from CFSPID to CF vary and risk factors for reclassification are not well established. We investigated whether clinical characteristics are associated with the risk of reclassification from CFSPID to a CF diagnosis.

METHODS

Children with a positive CF NBS were recruited from two sites in California. Retrospective, longitudinal, and cross-sectional data were collected. A subset of subjects had nasal epithelial cells collected for CF transmembrane conductance regulator (CFTR) functional assessment. Multivariate logistic regression was used to assess the risk of reclassification.

RESULTS

A total of 112 children completed the study (CF = 53, CFSPID = 59). Phenotypic characteristics between groups showed differences in pancreatic insufficiency prevalence, immunoreactive trypsinogen (IRT) levels, and Pseudomonas aeruginosa (PSA) colonization. Spirometry measures were not different between groups. Nasal epithelial cells from 10 subjects showed 7%-30% of wild-type (WT)-CFTR (wtCFTR) function in those who reclassified and 27%-67% of wtCFTR function in those who retained the CFSPID designation. Modeling revealed that increasing sweat chloride concentration (sw[Cl^- ]) and PSA colonization were independent risk factors for reclassification to CF.

CONCLUSION

Increasing sw[Cl^- ] and a history of PSA colonization are associated with the risk of reclassification from CFSPID to CF in a population with high IRT and two CFTR variants. A close follow-up to monitor phenotypic changes remains critical in this population. The role of CFTR functional assays in this population requires further exploration.

Cystic Fibrosis Screen Positive, Inconclusive Diagnosis Genotypes in People with Cystic Fibrosis from the U.S. Patient Registry

Rationale: Variants within the cystic fibrosis (CF) transmembrane conductance regulator gene, CFTR, that are of unknown significance or are categorized as non-CF causing may be observed in persons with CF. These variants are frequently detected in children with inconclusive newborn screen results and, in some cases, may be associated with a benign presentation in early childhood that progresses to a CF phenotype later in life. Objectives: To analyze data from individuals enrolled in the U.S. Cystic Fibrosis Foundation Patient Registry who have received a diagnosis of CF and who have variants found in a population of children with a CF screen positive, inconclusive diagnosis (CFSPID). Methods: This retrospective review analyzed registry data from individuals with a diagnosis of CF who also harbor one or more variants of interest because of their frequency within a CFSPID population and/or their interpretation as non-CF causing. Three groups were defined by the number of CF-causing variants identified (CF-Cx2, CF-Cx1, and CF-Cx0), which were reported in addition to the variant(s) of interest. Multivariate quantile regression modeling of the outcome for forced expiratory volume in 1 second (FEV1) generated a disease severity score for each person determined by six selected variables. Median scores were calculated for the three groups. Results: Patients carrying one CF-causing variant and at least one variant of interest (CF-Cx1) had higher median disease severity scores compared with those carrying CF-Cx2, suggesting a milder phenotype (P < 0.05). However, there was no statistically significant difference in scores between CF-Cx2 and the two other groups combined (CF-Cx1 and CF-Cx0; P = 0.33). Analysis revealed that the CF-Cx1 and CF-Cx0 groups, when compared with the CF-Cx2 group, had later median diagnoses (8 years vs. newborn; P < 0.0001), lower median sweat chloride (48 mmol/L vs. 94.5 mmol/L; P < 0.0001), lower prevalence of pancreatic insufficiency (29% vs. 78%; P < 0.0001), and higher median FEV1% predicted (95% vs. 87%; P = 0.0002). Conclusions: Individuals with CF who have specific variants frequently identified in children with CFSPID have a similar range of disease severity scores compared with those who have two CF-causing variants, but a milder phenotype overall. Variants that should be given careful scrutiny because of their high prevalence are G576A+R668C, T854T, R75Q, F1052V, R1070W, R31C, and L967S.

Diagnosing Cystic Fibrosis in Adults

Diagnosing cystic fibrosis (CF) in adulthood is not a rare occurrence for CF centers despite the popular belief that the diagnosis is achieved almost universally in childhood by means of newborn screening or early clinical presentation. The purpose of this review article is to highlight specific considerations of adult diagnosis of CF. Obtaining a diagnosis of CF at any age is exceptionally important to ensure optimal treatment, monitoring, and support. In the new era of more personalized treatment with the advent of transformative therapies targeting the underlying protein defect, accurate diagnosis is of increasing importance. This review highlights the diagnostic algorithm leading to a new diagnosis of CF in adults. The diagnosis is usually confirmed in the presence of a compatible clinical presentation, evidence of cystic fibrosis transmembrane conductance regulator (CFTR) protein dysfunction, and/or identification of variants in the CFTR gene believed to alter protein function. Achieving the diagnosis, however, is not always straightforward as CFTR protein function exists on a continuum with different organs displaying varying sensitivity to diminution in function. We highlight the current knowledge regarding the epidemiology of CF diagnosed in adults and outline the various clinical presentations, including pulmonary and extrapulmonary, which are more common in this population. We expand on the stepwise testing procedures that lead to diagnosis, paying particular attention to additional levels of testing which may be required to achieve an accurate diagnosis. There continues to be an important need for both pulmonary and other specialists to be aware of the potential for later presentation of CF, as the improvements in treatment over decades have had large positive impacts on prognosis for people with this condition.

Clinical Consequences and Functional Impact of the Rare S737F CFTR Variant and Its Responsiveness to CFTR Modulators

S737F is a Cystic Fibrosis (CF) transmembrane conductance regulator (CFTR) missense variant. The aim of our study was to describe the clinical features of a cohort of individuals carrying this variant. In parallel, by exploiting ex vivo functional and molecular analyses on nasal epithelia derived from a subset of S737F carriers, we evaluated its functional impact on CFTR protein as well as its responsiveness to CFTR modulators. We retrospectively collected clinical data of all individuals bearing at least one S737F CFTR variant and followed at the CF Centre of Tuscany region (Italy). Nasal brushing was performed in cooperating individuals. At study end clinical data were available for 10 subjects (mean age: 14 years; range 1–44 years; 3 adult individuals). Five asymptomatic subjects had CF, 2 were CRMS/CFSPID and 3 had an inconclusive diagnosis. Ex vivo analysis on nasal epithelia demonstrated different levels of CF activity. In particular, epithelia derived from asymptomatic CF subjects and from one of the subjects with inconclusive diagnosis showed reduced CFTR activity that could be rescued by treatment with CFTR modulators. On the contrary, in the epithelia derived from the other two individuals with an inconclusive diagnosis, the CFTR-mediated current was similar to that observed in epithelia derived from healthy donors. In vitro functional and biochemical analysis on S737F-CFTR expressed in immortalized bronchial cells highlighted a modest impairment of the channel activity, that was improved by treatment with ivacaftor alone or in combination with tezacaftor/elexacaftor. Our study provide evidence towards the evaluation of CFTR function on ex vivo nasal epithelial cell models as a new assay to help clinicians to classify individuals, in presence of discordance between clinical picture, sweat test and genetic profile.

CFTR-Related Metabolic Syndrome: Genetic Variants Increasing Pancreatitis Risk in the Pediatric Puerto Rican Population

CFTR-related metabolic syndrome (CRMS) is a novel diagnosis due to widespread use of and advances in the newborn screening (NBS) process for cystic fibrosis (CF) in the United States of America, allowing for the diagnosis of asymptomatic children with CF. Before 2015, a large Puerto Rican pediatric population was not screened for CF in the NBS test. Studies have shown that patients presenting with idiopathic recurrent or chronic pancreatitis have an increased frequency of cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations. We present a retrospective chart review of 12 pediatric cases (n = 12) that were presented to an outpatient community clinic with clinical manifestations associated with CF. The pancreatic insufficiency prevalence (PIP) score was calculated on CFTR mutations. The mutations considered for the calculation of the PIP score were: F508del (c.1521_1523del), V201M (c.601G > A), I507del (c.1519_1521del), and L1335P (c.4004T > C). V201M mutation was classified as mild in both PIP scores, and a correlation with pancreatitis was noted. Clinical manifestations vary in cases with the V201M variant (c.601G > A). One case was diagnosed with CFTR-related disorder (CRD) and recurrent pancreatitis. It is important to consider CRMS or CRD as a differential diagnosis in the pediatric population of Puerto Rico due to the implications and increased risk of pancreatitis and other CF-related complications.

Correlation between CFTR variants and outcomes of ART in patients with CAVD in Central China

Biallelic variants in Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) are the main pathogenic factor of congenital absence of the vas deferens (CAVD), including congenital bilateral absence of the vas deferens (CBAVD) and congenital unilateral absence of the vas deferens (CUAVD). However, there are few reports about the correlation between CFTR variant and outcomes of assisted reproductive technology (ART) in CAVD patients of China. In this study, 104 patients with CAVD were recruited in Central China, and provided gene detection by the whole-exome sequencing, among them 69% (72/104) carried at least one variant in CFTR and one carried adhesion G protein-coupled receptor G2 (ADGRG2) variant. A total of 81 CAVD patients were treated with ART, of which 21 and 60 carried none or at least one variant in CFTR, respectively. The fertilization rate, cleavage rate, effective embryo rate, implantation rate, clinical pregnancy rate and live birth rate per fresh embryo transfer were compared between patients with and without CFTR variants. It was found that the ART outcomes had no significant difference whether the patients carried the CFTR variant or not. In addition, all of the offspring were healthy after follow-up. In conclusion, rare CFTR variants may play a major role in patients with CAVD in Central China, which were greatly different from other descent. There was no significant difference in ART outcomes in CAVD patients with or without CFTR variants. The limitations of this study were that there was no statistical analysis of the sperm quality through TESA and conclusions were relatively limited due to the small sample size of the study.

Non-pulmonary CFTR-related symptom improvement with ivacaftor in p.Phe508del/p.Arg117His (7T) cystic fibrosis

Diagnosis and management of CRMS/CFSPID and cystic fibrosis (CF) with mild phenotypes remains challenging, and this extends to expanding practice with the use of CFTR modulators. We describe a case of an 18-year-old man with p.F508del/p.Arg117His(7T) initially presenting with CRMS/CFSPID. He went on to be diagnosed with pancreatic sufficient CF with minimal lung disease. However, he has had significant CFTR-related symptoms with recurrent pancreatitis and chronic sinusitis. These non-pulmonary symptoms resolved following introduction of the CFTR modulator ivacaftor. Care for those with mild CF phenotypes, CRMS/CFSPID and those with CFTR-RD must be individualized, and open dialogue, education and patient centred care is necessary to ascertaining which patients might benefit from management in a multidisciplinary CF clinic and treatment. There may be a role for expanding the use of CFTR modulators to include non-pulmonary manifestations of CFTR dysfunction in some cases.

Standards of care for CFTR variant-specific therapy (including modulators) for people with cystic fibrosis

Cystic fibrosis (CF) has entered the era of variant-specific therapy, tailored to the genetic variants in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene. CFTR modulators, the first variant-specific therapy available, have transformed the management of CF. The latest standards of care from the European CF Society (2018) did not include guidance on variant-specific therapy, as CFTR modulators were becoming established as a novel therapy. We have produced interim standards to guide healthcare professionals in the provision of variant-specific therapy for people with CF. Here we provide evidence-based guidance covering the spectrum of care, established using evidence from systematic reviews and expert opinion. Statements were reviewed by key stakeholders using Delphi methodology, with agreement (≥80%) achieved for all statements after one round of consultation. Issues around accessibility are discussed and there is clear consensus that all eligible people with CF should have access to variant-specific therapy.

Different management approaches and outcome for infants with an inconclusive diagnosis following newborn screening for cystic fibrosis (CRMS/CFSPID) and Pseudomonas aeruginosa isolation

INTRODUCTION

Evidence is currently lacking to guide the management of cystic fibrosis (CF) transmembrane conductance regulator-related metabolic syndrome CF screen-positive inconclusive diagnosis (CRMS/CFSPID) with Pseudomonas aeruginosa (Pa)-positive respiratory culture. This study assessed the clinical data, management, and outcomes of an Italian cohort of CRMS/CFSPID infants with Pa isolated from their airways.

METHODS

Data of Pa-positive CRMS/CFSPID infants born between January 2011 and August 2018 and followed at five CF Italian centres were retrospectively extracted. Further data were collected until June 2021 to assess outcomes, prevalence of subjects treated with antimicrobials, and treatment type and duration.

RESULTS

Forty-three asymptomatic CRMS/CFSPID patients (median age on 30 June 2021, 82 months; interquartile range [IQR], 63-98 months) with at least one positive airway culture for non-mucoid Pa (median age at first isolation, 18.7 months; IQR, 7-25 months) were enrolled. Of them, 24 (55.8%) underwent anti-Pa therapy. Pa clearance occurred in 22 (91.6%) of 24 patients versus spontaneous clearance in 16 of 19 (84.2%) untreated patients (chi-square, 0.5737; p = 0.44878). After a median follow-up of 6.2 years (IQR, 3.0-9.9), 7 (16.3%) were diagnosed with CF after a pathological sweat test (median age, 43 months; IQR, 28-77 months), 3 (7%) developed recurrent pancreatitis or isolated bronchiectasis consistent with CFTR-related disorder, and the CRMS/CFSPID classification remained in 33 (76.7%).

CONCLUSIONS

Pa detection frequently occurs in asymptomatic infants with CRMS/CFSPID but tends to clear spontaneously. More studies are needed to determine if Pa isolation can predict evolution.

The multi-faceted nature of 15 CFTR exonic variations: Impact on their functional classification and perspectives for therapy

BACKGROUND

The majority of variants of unknown clinical significance (VUCS) in the CFTR gene are missense variants. While change on the CFTR protein structure or function is often suspected, impact on splicing may be neglected. Such undetected splicing default of variants may complicate the interpretation of genetic analyses and the use of an appropriate pharmacotherapy.

METHODS

We selected 15 variants suspected to impact CFTR splicing after in silico predictions on 319 missense variants (214 VUCS), reported in the CFTR-France database. Six specialized laboratories assessed the impact of nucleotide substitutions on splicing (minigenes), mRNA expression levels (quantitative PCR), synthesis and maturation (western blot), cellular localization (immunofluorescence) and channel function (patch clamp) of the CFTR protein. We also studied maturation and function of the truncated protein, consecutive to in-frame aberrant splicing, on additional plasmid constructs.

RESULTS

Six of the 15 variants had a major impact on CFTR splicing by in-frame (n = 3) or out-of-frame (n = 3) exon skipping. We reclassified variants into: splicing variants; variants causing a splicing defect and the impairment of CFTR folding and/or function related to the amino acid substitution; deleterious missense variants that impair CFTR folding and/or function; and variants with no consequence on the different processes tested.

CONCLUSION

The 15 variants have been reclassified by our comprehensive approach of in vitro experiments that should be used to properly interpret very rare exonic variants of the CFTR gene. Targeted therapies may thus be adapted to the molecular defects regarding the results of laboratory experiments.

Diagnostic agreement among experts assessing adults presenting with possible cystic fibrosis: need for improvement and implications for patient care

Background

Increasing awareness of milder presentations of cystic fibrosis (CF) and greater interest in non-CF bronchiectasis are likely to lead to more CF screening by respiratory clinicians. As a result, adults who may not strictly fulfil CF diagnostic criteria yet display evidence of abnormal CF transmembrane conductance regulator (CFTR) function are being identified. The degree of agreement on diagnosis and care needs in these cases between CF clinicians remains unknown, and has implications for patient care, including access to CFTR modulator therapies.

Methods

We surveyed adult CF physicians in Canada, the USA, the UK and Ireland, and presented them with anonymised vignettes of adult patients referred for assessment of possible CF. Diagnostic inter-rater agreement over diagnosis, ease of classifying cases and appropriate follow-up was assessed using Krippendorff's reliability coefficient (α).

Results

Agreement over diagnosis (α=0.282), ease of classification (α= -0.01) and recommended follow-up (α=0.054) was weak. Clinician experience (>10 and 5-10 years versus <5 years) and location (UK and Ireland versus Canada) were associated with higher odds of recommending further testing compared with selecting a formal diagnosis (respectively, OR 2.87; p=0.022, OR 3.74; p=0.013 and OR 3.16; p=0.007). A modified standard of care was recommended in 28.7% of cases labelled as CF. 70% of respondents agreed with the statement that "Accurate distinction between CF and CFTR-related disorder has become significantly more pertinent with the advent of highly effective CFTR modulators".

Conclusions

Our results demonstrate low diagnostic concordance among CF specialists assessing cases of possible adult CF and highlight an area in need of improvement.

CFTR gene variants, air pollution, and childhood asthma in a California Medicaid population

Carriers of the cystic fibrosis transmembrane conductance regulator (CFTR) gene ("carriers") have been found to have an increased risk of persistent asthma. However, it is unclear at what level of CFTR function this risk exists and whether it is modified by asthmogens, such as air pollution. We conducted a retrospective cohort study of children born in California between July 2007 and December 2013, linking CFTR genotype data from the California newborn screening program to Medicaid claims records through March 17, 2020 to identify asthma cases, and to air pollution data from CalEnviroScreen 3.0 to identify levels of particulate matter with diameter 2.5 microns or smaller (PM_2.5 ). Log-binomial regression models for asthma risk were fitted, adjusting for race/ethnicity and sex. Compared to population controls, carriers had higher risk of asthma (adjusted risk ratio (aRR) = 1.29, 95% confidence interval (CI): 0.98, 1.69; p < 0.1). Other non-CF-causing variants on the second allele did not appear to further increase risk. Genotypes with the greatest asthma risk were F508del with an intron 10 T7 or (TG)11T5 in trans (aRR=1.52, 95% CI: 1.10, 2.12). This association was higher among children living in areas at or above (aRR = 1.80) versus below (aRR = 1.37) the current national air quality standard for PM_2.5 , though this difference was not statistically significant (p_interaction  > 0.2). These results suggest carriers with CFTR functional levels between 25% and 45% of wildtype are at increased risk of asthma. Knowledge of CFTR genotype in asthmatics may be important to open new CFTR-related treatment options for these patients.

Corneal Refractive Surgery Considerations in Patients with Cystic Fibrosis and Cystic Fibrosis Transmembrane Conductance Regulator-Related Disorders

This article discusses common ocular manifestations of cystic fibrosis (CF) and cystic fibrosis transmembrane conductance regulator-related disorders (CFTR-RD). A structured approach for assessing and treating patients with CF/CFTR-RD seeking corneal refractive surgery is proposed, as well as a novel surgical risk scoring system. We also report two patients with various manifestations of CFTR dysfunction who presented for refractive surgery and the outcomes of the procedures. Surgeons seeking to perform refractive surgery on patients with CF/CFTR-RD should be aware of mild to severe clinical manifestations of CFTR dysfunction. Specific systemic and ocular manifestations of CF include chronic obstructive pulmonary disease (COPD), bronchiectasis, recurrent pulmonary infections, CF-related diabetes and liver disease, pancreatic insufficiency, conjunctival xerosis, night blindness, meibomian gland dysfunction (MGD), and blepharitis. Corneal manifestations include dry eye disease (DED), punctate keratitis (PK), filamentary keratitis (FK), xerophthalmia, and decreased endothelial cell density and central corneal thickness. Utilization of the appropriate review of systems (ROS) and screening tests will assist in determining if the patient is a suitable candidate for refractive surgery, as CF/CFTR-RD can impact the health of the cornea. Collaboration with other medical professionals who care for these patients is encouraged to ensure that their CF/CFTR-RD symptoms are best controlled via systemic and other treatment options. This will assist in reducing the severity of their ocular manifestations before and after surgery.

Heterogeneous spectrum of CFTR gene mutations in Chinese patients with CAVD and the dilemma of genetic blocking strategy

In brief

The genetic heterogeneity of CFTR gene mutations in Chinese patients with congenital absence of the vas deferens (CAVD) differs from the hotspot mutation pattern in Caucasians. This paper reviews and suggests a more suitable screening strategy for the Chinese considering the dilemma of CFTR genetic blocking.

Abstract

Congenital absence of the vas deferens (CAVD) is a major cause of obstructive azoospermia and male infertility, with CFTR gene mutation as the main pathogenesis. Other genes such as ADGRG2, SLC9A3, and PANK2 have been discovered and proven to be associated with CAVD in recent studies. Multiple CFTR hotspot mutations have been found in Caucasians in several foreign countries, and relevant genetic counseling and preimplantation genetic diagnosis (PGD) have been conducted for decades. However, when we examined research on Chinese CAVD, we discovered that CFTR mutations show heterogeneity in the Chinese Han population, and there is currently no well-established screening strategy. Therefore, we have reviewed the literature, combining domestic and international research as well as our own, aiming to review research progress on the CFTR gene in China and discuss the appropriate scope for CFTR gene detection, the detection efficiency of other CAVD-related genes, and the screening strategy applicable to the Chinese Han population. This study provides more valuable information for genetic counseling and a theoretical basis for PGD and treatment for couples with CAVD when seeking reproductive assistance.

Clinical Utility of Medical Exome Sequencing: Expanded Carrier Screening for Patients Seeking Assisted Reproductive Technology in China

Purpose: Expanded carrier screening (ECS) is an effective method to identify at-risk couples (ARCs) and avoid birth defects. This study aimed to reveal the carrier spectrum in the Chinese population and to delineate an expanded carrier gene panel suitable in China.

Methods: Medical exome sequencing (MES), including 4,158 disease-causing genes, was offered to couples at two reproductive centers. It was initially used as a diagnostic yield for potential patients and then used for ECS. Clinical information and ECS results were retrospectively collected.

Results: A total of 2,234 couples, representing 4,468 individuals, underwent MES. In total, 254 individuals showed genetic disease symptoms, and 56 of them were diagnosed with genetic diseases by MES. Overall, 94.5% of them were carriers of at least one disease-causing variant. The most prevalent genes were GJB2 for autosomal recessive disorders and G6PD for X-linked diseases. The ARC rate was 9.80%, and couples were inclined to undergo preimplantation genetic testing when diseases were classified as “profound” or “severe.”

Conclusion: This study provided insight to establish a suitable ECS gene panel for the Chinese population. Disease severity significantly influenced reproductive decision-making. The results highlighted the importance of conducting ECS for couples before undergoing assisted reproductive technology.

Personalized medicine with drugs targeting the underlying protein defect in cystic fibrosis: is monitoring of treatment response necessary?

Cystic fibrosis (CF) is caused by two mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene. In the last years, drugs targeting the underlying protein defect like lumacaftor/ivacaftor (LUM/IVA) or tezacaftor/ivacaftor (TEZ/IVA) and more recently elexacaftor/tezacaftor/ivacaftor (ELX/TEZ/IVA) were admitted. Outcome parameters evaluating therapy response like forced expiratory pressure in 1 s (FEV1), body mass index (BMI) or the efficacy of CFTR function in sweat glands showed improvement in several cases. Other, CFTR biomarkers were analysed rarely. This prospective observational study was aimed at evaluating CFTR function in patients treated with different CFTR modulators together with common valid clinical outcome parameters at standardized appointments (day 0, week 2, 4, 16). We followed four patients with the same mutation (F508del-CFTR), sex, age and disease severity. Monitoring focused on lung function, gastrointestinal aspects and CFTR function of sweat glands, nasal and intestinal epithelium. Sweat tests were performed by pilocarpine iontophoresis. Nasal potential difference (NPD) measured transepithelial voltage in vivo and potential increased when CFTR function improved. Rectal biopsies were obtained for intestinal current measurements (ICM) ex vivo. Intestinal CFTR function was assessed by stimulating chloride secretion with different reagents. Response to CFTR modulators regarding clinical outcome parameters was rather variable. A sweat chloride reduction of 35.3 mmol/L, nasal CFTR rescue of 4.4% and fivefold higher CFTR function in the intestine was seen at week 16 post-LUM/IVA. Due to our monitoring, we identified a non-responder to LUM/IVA and TEZ/IVA. In case of ELX/TEZ/IVA, clinical parameters and CFTR bioassays improved and were concordant. Although our cohort is small, results emphasize that non-responders exist and conclusions could not be drawn if patients were not monitored. Data on CFTR function can confirm or disprove ongoing CFTR dysfunction and might be helpful selectively. Non-responders need other alternative therapy options as demonstrated with ELX/TEZ/IVA.

Dornase alfa in Cystic Fibrosis: indications, comparative studies and effects on lung clearance index

Cystic fibrosis (CF) is the most common inherited disease in Caucasian populations, affecting around 50,000 patients in Europe and 30,000 in United States. A mutation in CF trans-membrane conductance regulator (CFTR) gene changes a protein (a regulated chloride channel), which is expressed in many tissues. Defective CFTR results in reduced chloride secretion and an overage absorption of sodium across the epithelia, leading to thickened secretions in organs such as pancreas and lung. Gradually, there have been considerable improvements in the survival of people with CF, thanks to substantial changes in specialized CF care and the discovery of new CFTR modulators drugs. Nevertheless, lung disease remains the most common cause of death. For these reasons improvement of sputum clearance is a major therapeutic aim in CF. So far, symptomatic mucolytic therapy is mainly based on inhalation of dornase alfa, hypertonic saline or mannitol, in combination with physiotherapy. The major component of mucus in CF is pus including viscous material such as polymerized DNA derived from degraded neutrophils. Dornase alfa cleaves the DNA released from the neutrophils and reduces mucous viscosity, and further prevent airway infections and damage to the lung parenchyma. In this review we will summarize the current knowledge on dornase alfa in the treatment of CF lung disease, especially highlighting the positive effect on lung clearance index, a sensitive measure of ventilation inhomogeneity.

No Stone Left Unturned: Pediatric Pancreatic Stones Presenting With Obstructive Jaundice

Pancreatic lithiasis, the formation of calcifications in the pancreatic duct, occurs uncommonly in pediatric patients but can occur more frequently with chronic pancreatitis (CP). Cystic fibrosis (CF) is one of the major causes of pancreatic lithiasis in pediatric patients, with mutations in the CF transmembrane conductance regulator (CFTR) gene reported in up to 23% of pediatric CP patients. Mutations in the CFTR gene can lead to mild cases of CF, which may delay diagnosis and treatment. In such cases, pancreatitis can be the presenting symptom in children with CF. We report a unique case of a 10-year-old female with previously undiagnosed and untreated CF presenting with abdominal pain, vomiting, and obstructive jaundice. Her pancreatic lithiasis and biliary obstruction were successfully treated with endoscopic retrograde cholangiopancreatography (ERCP).

Determination of Cystic Fibrosis Mutation Frequency in Preterm and Term Neonates with Respiratory Tract Problems

Cystic fibrosis (CF) is an autosomal recessive disease. The genetic transition occurs with CF transmembrane conductance regulator (CFTR) gene mutation. We aimed to determine the frequency of CF mutations and also new mutations in the CFTR gene in neonates with respiratory distress. Newborn babies hospitalized due to respiratory distress were included in the patient group. The control group consisted of infants who had no respiratory distress. The CFTR genes of both groups were analyzed using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) methods. A total of 40 patients (20 in the patient group and 20 in the control group) were evaluated. The CFTR gene analysis was normal in 16 neonates in the patient group, whereas in others: A46D (c.137C>A) (n = 1), D1312G (c.3935A>G) (n = 1), R117H (c.350G>A) (n = 1), S1426P (c.4276T>C) (n = 1) heterozygotes were detected; CFTR gene analysis was normal at 14 neonates in the control group, whereas in others: E1228G (c.3683A>G) (n = 1), E217G (c.650A>G) (n = 1), E632TfsX9 (c1894_1895delAG) (n = 1), I807M (c.2421 A>G) (n = 2), S573F (c.1718C>T) (n = 1) heterozygotes were detected. There was no significant difference in the patient and control groups’ CFTR gene analysis (p = 0.340). This study demonstrates the importance of CFTR gene analysis in asymptomatic newborn infants for follow-up and early diagnosis of CFTR-related disorders. In this study, a c.1894_1895delAG (E632TfsX9) heterozygous mutation detected in the CFTR gene in an asymptomatic newborn infant, was first encountered in the literature.

Revisiting a diagnosis of cystic fibrosis - Uncertainties and considerations

There is now increased knowledge and experience of newborn screening around the world. There is also a better understanding of CF gene analysis, informed by international databases. This has resulted in a small number of children and adults having their diagnosis of CF reversed. This article illustrates this issue with three cases. It considers how best to tell children and adults with their families, and the reactions that may be encountered. It also discusses practical issues of removing the diagnosis.

Cystic fibrosis transmembrane conductance regulator (CFTR): beyond cystic fibrosis

Background

The cystic fibrosis transmembrane conductance regulator (CFTR) gene has been traditionally linked to cystic fibrosis (CF) inheritance in an autosomal recessive manner. Advances in molecular biology and genetics have expanded our understanding of the CFTR gene and its encoding products expressed in different tissues.

Aim

The study’s aim consists of reviewing the different pathological CF phenotypes using the existing literature. We know that alterations of the CFTR protein’s structure may result in different pathological phenotypes.

Methods

Open sources such as PubMed and Science Direct databases have been used for this review. We focused our selection on articles published within the last 15 years. Critical terms related to the CFTR protein have been used: “CFTR AND cancer,” “CFTR AND celiac disease,” “CFTR AND pancreatitis,” “children,” “adults,” “genotype,” “phenotype,” “correlation,” “mutation,”  “CFTR,” “diseases,” “disorders,” and “no cystic fibrosis.”

Results

We analyzed 1,115 abstracts in total. Moreover, only 189 were suitable for the topic. We focused on the role of CFTR in cancer, gastrointestinal disorders, respiratory diseases, reproductive system, and systemic hypertension.

Conclusions

Mutations in CFTR gene are often associated with CF. In this review, we highlighted the broad spectrum of alterations reported for this gene, which may be involved in the pathogenesis of other diseases. The importance of these new insights in the role of CFTR relies on the possibility of considering this protein/gene as a novel therapeutic target for CF- and CFTR-related diseases.

Complex Presentation of Hao-Fountain Syndrome Solved by Exome Sequencing Highlighting Co-Occurring Genomic Variants

Objective: The co-occurrence of pathogenic variants has emerged as a relatively common finding underlying complex phenotypes. Here, we used whole-exome sequencing (WES) to solve an unclassified multisystem clinical presentation. Patients and Methods: A 20-year-old woman affected by moderate intellectual disability (ID), dysmorphic features, hypertrichosis, scoliosis, recurrent bronchitis, and pneumonia with bronchiectasis, colelithiasis, chronic severe constipation, and a family history suggestive of autosomal dominant recurrence of polycystic kidney disease was analyzed by WES to identify the genomic events underlying the condition. Results: Four co-occurring genomic events fully explaining the proband’s clinical features were identified. A de novo truncating USP7 variant was disclosed as the cause of Hao–Fountain syndrome, a disorder characterized by syndromic ID and distinctive behavior. Compound heterozygosity for a major cystic fibrosis-causing variant and the modulator allele, IVS8-5T, in CFTR explained the recurrent upper and lower respiratory way infections, bronchiectasis, cholelithiasis, and chronic constipation. Finally, a truncating PKD2 variant co-segregating with polycystic kidney disease in the family allowed presymptomatic disease diagnosis. Conclusions: The co-occurring variants in USP7 and CFTR variants explained the multisystem disorder of the patient. The comprehensive dissection of the phenotype and early diagnosis of autosomal dominant polycystic kidney disease allowed us to manage the CFTR-related disorder symptoms and monitor renal function and other complications associated with PKD2 haploinsufficiency, addressing proper care and surveillance.